Based on the bestselling fantasy book series “A Song of Ice and Fire” by George R. R. Martin, HBO’s “Game of Thrones” concluded its 10-episode third season in June and will begin filming its fourth season this summer. The series, executive produced and written by David Benioff and D. B. Weiss, is an epic story of treachery and nobility, set on the continent of Westeros, where summers and winters can last years.